This invention relates to a rotary electric machine such as a fan motor or the like, and more particularly to a coupling structure between an insulator of a stator and a bearing holder.
A conventional fan motor which has been known in the art is generally constructed in such a manner that a rotor including a plurality of permanent magnets is rotated about a revolving shaft with respect to a stator including a plurality of salient poles. In the conventional fan motor thus constructed, the stator is mounted on a bearing holder in which at least one bearing for supporting the revolving shaft is fitted. Also, an insulator which is made of a synthetic resin material is arranged so as to cover a part of an outer surface of a stator core of the stator. Further, a coupling structure is provided so as to couple the insulator and bearing holder to each other to prevent relative movement between the bearing holder and the stator in both an axial direction of the revolving shaft and a peripheral direction thereof. For example, a motor disclosed in Japanese Patent No. 2,778,894 and U.S. Pat. No. 5,650,678 corresponding thereto is so configured that a bearing holder is deformed at a forward end thereof toward an insulator by heating, to thereby prevent relative movement between the bearing holder and a stator in an axial direction of a revolving shaft. Also, in the conventional fan motor described above, the bearing holder is provided on an outer periphery thereof with a projection and correspondingly the insulator is provided with a fitted section in which the projection of the bearing holder is fitted. Such construction effectively prevents relative movement between the bearing holder and the stator in the peripheral direction of the revolving shaft.
However, the bearing holder is often substantially varied in thickness during formation of the bearing holder by injection molding of a synthetic resin material or the like. Such a variation in thickness of the bearing holder leads to a so-called resin escaping or receding phenomenon which causes escaping or receding of the synthetic resin material during curing of the synthetic resin. When such a resin receding phenomenon substantially occurs at a portion of the bearing holder on which the bearing is held, the bearing holder is deteriorated in accuracy of an inner diameter thereof or varied in inner diameter. This causes deviation between a center of rotation of the bearing and that of the bearing holder to be increased, leading to vibration of the fan motor, so that it is deteriorated in durability.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a rotary electric machine or machinery which is capable of permitting coupling between a bearing holder and an insulator to be carried out without causing a deterioration in accuracy of an inner diameter of a portion of the bearing holder on which the bearing is held.
It is another object of the present invention to provide a fan motor which is capable of permitting coupling between a bearing holder and an insulator to be carried out without deteriorating accuracy of an inner diameter of a portion of the bearing holder on which the bearing is held.
It is a further object of the present invention to provide a rotary electric machine which is capable of ensuring reliable coupling between a bearing holder and an insulator.
It is still another object of the present invention to provide a rotary electric machine which is capable of facilitating coupling between a bearing holder and an insulator due to deformation by heating.
It is yet another object of the present invention to provide a rotary electric machine which is capable of permitting application of any unnecessary stress from an insulator to a bearing holder to be effectively prevented by deformation of a plurality of projections provided on the insulator.
In accordance with the present invention, a rotary electric machine is provided. The rotary electric machine includes a rotor rotated about a revolving shaft arranged so as to extend in an axial direction thereof. Also, the rotary electric machine includes a bearing holder made of a synthetic resin material and constructed into a hollow structure. The bearing holder has a forward end positioned on one of both sides defined along an axis of the revolving shaft (hereinafter referred to as xe2x80x9cone axial sidexe2x80x9d) and a rearward end positioned on the other of both sides defined along the axis of the revolving shaft and opposite to the one axial side (hereinafter referred to as xe2x80x9cthe other axial sidexe2x80x9d). Also, the bearing holder is coupled at the rearward end thereof to a casing and has at least one bearing for supporting the revolving shaft fitted therein. The rotary electric machine also includes a stator including a stator core, an insulator and a plurality of windings. The stator core is formed at a central portion thereof with a through-hole via which the bearing holder extends and includes a plurality of salient poles arranged on an outer periphery thereof so as to be spaced from each other at predetermined intervals in a peripheral direction of the revolving shaft. The insulator is made of a synthetic resin material exhibiting electrical insulating properties and arranged so as to cover a part of an outer surface of the stator core while keeping a magnetic pole surface of each of the salient poles of the stator core and an inner surface of the through-hole exposed. The windings each are formed by winding a conductive wire on each of the salient poles through the insulator. The rotary electric machine further includes a coupling structure for coupling the bearing holder and insulator to each other to prevent relative movement between the bearing holder and the stator in the axial direction of the revolving shaft and relative movement between the stator and the bearing holder in the peripheral direction of the revolving shaft. The coupling structure is constituted by at least one recess formed on the forward end of the bearing holder projecting through the through-hole of the stator core so as to be open on the one axial side and in a radial direction of the revolving shaft, as well as at least one projection provided on the insulator and tightly fitted in the recess of the bearing holder while keeping the bearing holder fully fitted in the through-hole of the stator core. The term xe2x80x9ctightly fittedxe2x80x9d or xe2x80x9ctight fittingxe2x80x9d as used herein is intended to mean fitting which is not readily released due to vibration or the like or which prevents the projection and recess fitted together from being readily disengaged from each other due to vibration or the like. Alternatively, the projection of the insulator may be press-fitted in the recess of the bearing holder. The term xe2x80x9cpress-fittedxe2x80x9d or xe2x80x9cpress fittingxe2x80x9d as used herein is intended to mean fitting carried out by forcibly fitting the projection in the recess by means of force at an increased magnitude, to thereby couple both to each other while deforming the projection and recess. However, tight fitting or press fitting is not necessarily employed when the projection and recess are deformed at a periphery thereof by heating, to thereby be coupled to each other as described hereinafter.
In the rotary electric machine of the present invention, it is merely required that the bearing holder is formed on the forward end thereof with the recess. This eliminates a necessity of substantially varying a thickness of the end of the bearing holder, resulting in effectively preventing a synthetic resin material of the bearing holder from escaping or receding which occurs at or near the forward end of the bearing holder when the bearing holder is made of the synthetic resin material. Thus, the present invention effectively prevents a deterioration in accuracy of a diameter of an inner periphery of the forward end of the bearing holder.
Also, in the present invention, the projection of the insulator is arranged in correspondence to the forward end of the bearing holder which is an end of the bearing holder on a side on which the stator is inserted into the bearing holder. This permits the stator to be readily inserted into the bearing holder without being obstructed by the projection. Also, it effectively prevents relative movement between the bearing holder and the stator in the peripheral direction of the revolving shaft as well as in the axial direction thereof.
Coupling between the bearing holder and the insulator may be carried out by only tight fitting between the projection and the recess or press fitting therebetween. Alternatively, in order to enhance reliability of the fitting, the projection of the insulator and the recess of the bearing holder are preferably subjected at a periphery thereof to deformation by heating, to thereby be coupled to each other while keeping the projection fitted in the recess. This further enhances coupling between the bearing holder and the insulator, resulting in the coupling being attained with increased reliability.
In this instance, deformation of the periphery by heating may be carried out so as to bend it outwardly in a radial direction of the revolving shaft. This permits the deformed projection and recess to form a hook in cooperation with each other. The hook thus formed permits forward movement of the insulator or movement thereof toward the one axial side to be more effectively prevented. In order to further enhance the advantage, it is preferable that a plurality of the projections and a plurality of portions of the forward end of the bearing holder defined between the respective adjacent two of a plurality of the recesses are deformed by heating so as to be bent outwardly in the radial direction of the revolving shaft while keeping the projections fitted in the recesses.
The recesses are preferably arranged on the forward end of the bearing holder while being spaced from each other at substantially equal intervals in the peripheral direction of the revolving shaft. Such arrangement permits spots at which the coupling is carried out to be scattered in the peripheral direction of the revolving shaft, to thereby prevent breakage of the coupling due to application of undue force thereto.
The insulator is generally constituted by two insulator halves respectively fitted on both sides of the stator core defined in the axial direction of the revolving shaft. One of the insulator halves which is positioned on the one axial side defined along the axis of the revolving shaft while keeping the bearing holder fully fitted in the through-hole of the stator includes a raised wall extending toward the one axial side from an end surface of the stator core positioned on the one axial side defined along the axis of the revolving shaft. The raised wall is integrally formed on an inner surface thereof with the projections in a manner to be spaced from each other at substantially equal intervals in the peripheral direction of the revolving shaft and project in the radial direction of the revolving shaft. The raised wall is formed into a substantially cylindrical shape and arranged so as to be concentric with the bearing holder. The raised wall is formed into an inner diameter which permits the forward end of the bearing holder to be fitted in the raised wall. The raised wall is integrally provided at a portion thereof positioned rather on the one axial side with the projections in a manner to project on the one axial side and inwardly in the radial direction of the revolving shaft. The bearing holder is subjected at a portion thereof projecting on the one axial side and beyond the raised wall to deformation by heating so as to be bent outwardly in the radial direction of the revolving shaft, resulting in being abutted against a forward end surface of the raised wall.
The raised wall preferably includes a cylindrical extension extending along the one axial direction component as compared with the projections. Arrangement of such an extension prevents deformation of a wall of the stator surrounding the windings in spite of deformation of the projections by heating.
The raised wall is preferably formed on the inner surface thereof with slits so as to be positioned between respective adjacent two of the projections and open on the side of the one axial direction component and in the radial direction. Formation of such slits permits periphery portions of the deformed recesses of the bearing holder to be entered into the slits when the projections and the periphery portions of the recesses of the bearing holder are deformed by heating. This further enhances coupling between the bearing holder and the insulator.
The bearing holder and casing may be formed so as to be integral with each other. Alternatively, they may be formed separate from each other.
The present invention may be practiced in the form of a fan motor. In accordance with this aspect of the present invention, a fan motor is provided. The fan motor includes a rotor rotated about a revolving shaft arranged so as to extend in an axial direction thereof; an impeller mounted on the rotor; a casing made of a synthetic resin material and including a frame having a wind tunnel formed therein in which the impeller is rotated, a motor housing and a plurality of webs for connecting the frame and motor housing to each other; and a bearing holder made of a synthetic resin material by injection molding and constructed into a hollow structure. The bearing holder has a forward end positioned on one axial side defined along an axis of the revolving shaft and a rearward end positioned on the other axial side defined along the axis of the revolving shaft. The bearing holder is coupled at the rearward end thereof to the motor housing of the casing and has at least one bearing for supporting the revolving shaft fitted therein. The fan motor further includes a stator including a stator core, an insulator and a plurality of windings. The stator core is formed at a central portion thereof with a through-hole via which the bearing holder extends and includes a plurality of salient poles arranged on an outer periphery thereof so as to be spaced from each other at predetermined intervals in a peripheral direction of the revolving shaft. The insulator is made of a synthetic resin material exhibiting electrical insulating properties and arranged so as to cover a part of an outer surface of the stator core while keeping a magnetic pole surface of each of the salient poles of the stator core and an inner surface of the through-hole exposed. The windings each are formed by winding a conductive wire on each of the salient poles through the insulator. The fan motor further includes a coupling structure for coupling the bearing holder and insulator to each other to prevent relative movement between the bearing holder and the stator in the axial direction of the revolving shaft and relative movement between the stator and the bearing holder in the peripheral direction of the revolving shaft. The coupling structure is constituted by a plurality of recesses formed on the forward end of the bearing holder projecting via the through-hole of the stator core so as to be open on the one axial side and in a radial direction of the revolving shaft, as well as a plurality of projections provided on the insulator and respectively fitted in the recesses of the bearing holder while keeping the bearing holder fully fitted in the through-hole of the stator core. The projections and recesses are deformed at a periphery thereof by heating, to thereby be coupled to each other while keeping the projections respectively fitted in the recesses. The forward end of the bearing holder is deformed at a portion thereof positioned between each adjacent two of the recesses by heating, to thereby be bent outwardly in the radial direction of the revolving shaft.